This invention relates generally to apparatus for resistivity mapping of the earth""s surface, and more particularly the invention relates to a tow mechanism for use by a human operator in towing such apparatus over the surface of the earth to obtain resistivity measurements.
Resistivity measuring apparatus is known for measuring electrical properties of rock and soil. As described in co-pending application Ser. No. 09/270,132 (U.S. Pat. No. 6,037,784), supra, the resistivity of a material can be determined by passing a current through the material at one pair of electrodes and measuring received voltage at another pair of electrodes. This is a common practice in geophysical measurements in which a transmitter applies an alternating current to the ground through a first electrode structure, and voltage at the transmission frequency is detected by a receiver through a second electrode structure on the ground and spaced from the first electrode structure. The detected current is a measure of soil resistivity, assuming the transmitter power level (voltage, current) is known.
Typically, a coaxial-cable array with transmitter and receiver sections is pulled along the ground by a small vehicle, and electrical currents capacitively coupled to the ground from the transmitter are continuously detected by the receiver. The electrical properties are determined from the detected current as the apparatus traverses the surface.
The present invention is directed to resistivity mapping apparatus including a tow mechanism for use by a human operator in pulling the resistivity mapping apparatus across the surface.
In accordance with the invention resistivity mapping apparatus is provided for movement by a human operator across a surface and includes a transmitter with antenna electrode apparatus for coupling an electrical current to the earth surface, and at least one receiver including antenna electrode apparatus for receiving a signal from a transmitter antenna apparatus. A line such as rope serially connects the transmitter and receiver. The apparatus further includes a generally triangular shaped tow ring engageable by human operator, the tow ring having two opposing hooks at a vertex of the tow ring. A tow line engages the two opposing hooks of the tow ring and a cable depressor weight on the ground whereby the human operator can pull the cable depressor weight, transmitter and receiver over the earth surface.
In preferred embodiments the tow ring is engaged by a battery belt, harness, or suitable pack frame of the human operator. A signal transmission line in the tow line connects signals from the receiver to a data logger console carried by the human operator.
The invention and objects and features thereof will be more readily apparent from the following detailed description and appended claims when taken with the drawings.